Outline:

start for loop, iterating through files (https://www.geeksforgeeks.org/how-to-iterate-over-files-in-directory-using-python/)

use opencv to grab bottom right corner of image (https://stackoverflow.com/a/58984370)

convert the output to greyscale then binary

use pytesseract image-to-string on output to find page number (saving this to a variable inside the loop)

rename the input file to the page number variable

end loop